NIST APAR23 – Heating/mixed air damper control is overlapping (Mode 5 – Unknown Occupied Mode)

Applicable Systems

• NISTAPAR: APAR
• Primary: AHU, RTU, MUA, ERV

Objective/Method/Outcome

• Objective: Indicates that the HCV and MAD are operating at the same time during occupied hours.

• Method: Check if the HCV and MAD are operating at the same time for over 8 occupied hours per week while the unit is in Mode 5.

• Outcome: An insight is generated when the HCV and MAD are operating at the same time for over 8 occupied hours per week while the unit is in Mode 5.

Logic

If (MAD > 20% Modulating; Temperature Threshold && HCV > 2% Open) { return true; }

Inputs

• HCV {cmd, heat, water, valve } (Real Trend Log)
• AHU_MODE_CTL {ahu, mode} (Real Trend Log)
• MAD {cmd, mixed, air, damper} (Real Trend Log)

Parameters

Parameter	Expression Block Series Number	Description	Default Value (Units)
Const – MAD min	81	The minimum damper position to be considered open	20 (%)
HCV Error Threshold	70	The movement tolerance of the HCV. This is used to define when the valve is open -everything above the formula (100 – HCV Error Threshold) is considered saturated.	0 (%)
Const – Damper signal threshold	82	The movement tolerance of the MAD.	2 (%)
Acceptable Hours per Week	73	The amount of time that this error is allowable for the unit per week. Anything more than that time is considered a fault.	8 (h)